Voltage dropping system for phonographs with amplifiers



April 1957 J. R. SHOAF u 2,789,235

VOLTAGE DROPPING SYSTEM FOR PHONOGRAPHS WITH AMPLIFIERS Filed Nov. 18,1954 IN V EN TOR.

2,789,235 VOLTAGE DROPPING SYSTEM FOR PHONO- GRAPHS WITH AMPLIFIERSJames R. Shoat H, Collingswood, N. J., assignor to Radio Corporation ofAmerica, a corporation of Delaware Application November 18, 1954, SerialNo. 469,603 7 Claims. (Cl. 307-112) The present invention relates toelectric phonographs and more particularly to power supply circuits foruse with phonographs of the type which include audio frequency soundamplifiers and which are designed for operation from one or moredifferent power line voltages.

In general, and as used herein, an electric phonograph includes amechanical record playing apparatus driven by an electric motor and aself-contained audio frequency amplifier. In many instances it isdesirable that the phonograph be operable from one or more power linevoltages, the most commonly available voltages being 110 volts A. C. and220 volts A. C. The previous practice in 110/220 volt phonographs was toprovide a twowinding motor with the windings connected in parallel foruse with l10-volt power lines in series for 220-volt power lines. Theamplifiers were designed for 110-volt operation and one or more highwattage resistors were used to drop the 22% volts to 110 volts with theaccompanying power loss and heat problem in compact instruments. It ispossible to use transformers to change the power line voltages, but theaddition of a transformer to the phonograph not only increases the costof the equipment but adds to the size and weight with no appreciableadvantage in use.

It is an object of this invention to provide a simplified power supplycircuit for electric phonographs which is readily operable from one ormore power line voltages, with a high degree of eificiency.

It is another object of this invention to provide an improved phonographsystem operative on one or more power line voltages which utilizes onlycomponents already a part of an electrical phonograph designed foroperation from a single power line voltage.

It is a further object of this invention to provide an improved electricphonograph system which is operable from one or more power line voltageswith no unnecessary power loss and accompanying heat dissipationresulting therefrom.

it is still a further object of this invention to provide a simplifiedpower supply circuit for electric phonographs which may be manufacturedin large quantities at low cost and which has no unnecessary heatdissipation thereby permitting a more compact construction.

In accordance with the invention, the phonograph is provided with amotor having a pair of field windings which may be connected in parallelfor operation at a low voltage such as 110 volts, and in series foroperation at a higher voltage such as 220 volts. The audio frequencyamplifier which is self-contained in the phonograph, and designed tooperate from a single voltage, is connected across one of the fieldwindings. It is, of course, understood that the audio frequencyamplifier may be a portion of a signal receiver or the like in aradio-phonograph instrument. In effect the motor windings are used as anauto-transformer to supply the same operating voltage to the audiofrequency amplifier, which is provided with a fixed connectiontherewith, while only the motor windings are switched to conform to thesupply line voltage.

The novel features that are considered characteristic of this inventionare set forth with particularity in the pending claims. The inventionitself, however, both to its organization and method of operation, aswell as adited States Patent 'ice ditional objects and advantagesthereof, will best be understood from the following description whenread in connection with the accompanying drawing.

Referring to the sole figure, a single stage audio frequency amplifierhaving an amplifier tube 5, is connected between an electric phonographpickup device 6 and a sound reproducer or loud speaker 7 in aconventional phonograph amplifier circuit. Volume control means for thephonograph amplifier is indicated at 8 and includes a variable volumecontrol connection 9 for the amplifier tube 5 and an input voltagedropping resistor 19 between the pickup device and the volume controlelement 8.

The tube 5 may be of the filamentary type or of the cathode heater typeshown in the present example, in which the cathode 11 is provided with asuitable heater element 12.

The anode circuit of the amplifier 5 is connetced to one end of aprimary winding 13 of an output transformer to a source of operatingpotential +B which is connected to the tap 14 on the transformer. Thescreen electrode of the amplifier 5 is connected to the other end of theprimary winding 13 and to the source of operating potential +B at thetransformer tap 14.

The rectifier for supplying anode and other operating potentials to theamplifier is indicated at 16 and comprises an anode 17 which isconnected through a lead 18 to one side of the power supply line 19. Therectifier 16 also has a cathode 20 which is connected with the positiveanode supply lead 21 of the phonograph amplifier, through a filtercomprising a series resistor 22 and the usual shunt filter capacitor 23.The opposite side of the power supply line 24 is connected through anoperating switch 25 to a supply lead 26 which, in turn, is connected tosystem ground 27 thereby forming a return circuit for the anode andother operating supply circuits. The system ground 27 is provided by acommon wiring which is isolated from the chassis and is connectedthrough the capacitor 28 to the conductive chassis 29 on which theamplifier and record changer mechanism are mounted.

The rectifier is provided with a heater element 30 for the cathode 20which is connected in series with the cathode heater 12 for theamplifier tube 5 through a series resistor 32. This series circuit isconnected to the lead 18 which forms one side of the power supply lineand is connected through ground to the lead 26.

The electric motor for the electric phonograph turntable 35 has a pairof substantially similar field or operating windings 36 and 37 which areconnected to a manually operable double-pole, double-throw switch 38which provides a convenient means for alternatively connecting the fieldwindings in series or in parallel. The double-pole, double-throw switchhas a plurality of contact terminals 39, 40, 41, 42, 43 and 44 to whichthe field windings and power supply are connected. The winding 36 isconnected to a pair of terminals 39 and 44 respectively while thewinding 37 is connected to a pair of terminals 40 and 41. The or 220volt power line (not shown) is connected through a plug 45 and thesupply lines 24 and 19 to the terminals 39 and 41 of the switch 38, anda jumper is connected between the terminals 40 and 43.

For 220 volt operation the double-pole, double-throw switch is in theportion shown in solid line, wherein the terminal 44 is connected withthe terminal 40 while the terminal 39 is connected with the terminal 42.The field windings 36 and 37 are thus connected in series. Tracing thecircuit from the supply line 19 which is connected with the terminal 41,the winding 37 is connected from the terminal 41 to one side of thewinding 36 through the terminals 49 and 44. The other side of thewinding 36 is connected through the terminal 39 to the supply line 24. eIn the 220 volt position of the switch 38, the audio frequency amplifieris connected with the terminals 40 and 41 or directly in parallel withthe field winding 37. Since the total power line voltage is developedacross the series combination of the windings 36 and 37, the voltageacross either is substantially on half of the line voltage. Thus 110volts is'supplied to the audio frequency amplifier. The field windingsin effect act as a step-down auto-transformer in which the seriallyconnected windings 36 and 37 are connected across the 220 volt powerline and the audio frequency amplifier power supply is connected acrossthe winding 37.

For llo-volt operation the double-pole, double-throw switch 38 is movedto the position shown in the dotted lines, and the connections arebroken between the terminals 42 and 39 and 40 and 44 respectively. Thefield windings are thus connected in parallel. Tracing the circuit, thefield winding 37 is connected to the supply lead 19 at the'terminal 41and to the supply lead 24 through the terminals 43 and 39. The winding36 is connected to the power supply lead 24 at the terminal 39 and isconnected by way of the terminals 44 and 41 to the supply lead 19.

In the 110-volt position of the switch 30 the audio frequency amplifieris connected with the terminals 49 and 41 or in parallel with both thefield windings 36 and 37. Since the phonograph audio frequency amplifierwas designed to operate on 110 volts A. C., the 110 volt line voltagewhich is across the parallel-connected windings 36 and 37 'is availableto the amplifier. In other words the phonograph amplifier is directlyacross the llO-volt .power line through the lead 18 which is directlyconnected to the power supply lead 19, and the lead 26 which isconnected through the terminals 40, 43 and 39 to the lead 24.

Thus, by simply connecting the phonograph record .player motor fieldwindings in parallel or in series, the phonograph is conditioned foroperation from either 110 or 220 volts'A. C. power source, theself-contained amplifier or the line being'at all times connected inparallel with one of the field windings,'and in either case beingenergized by 110 volts A.'C. It should be understood that the inventionis not restricted to the particular voltages'men- 'tioned, but'is-applicable to other A. C. voltages.

An electric phonograph system constructed in accordance with theinvention does not require any special. components such as a motor withspecial field windings or voltage dropping resistors or the like. Themotor used with the phonograph of the invention can be manufacturedforsubstantially the same cost as the motors ordinarily used withphonographs for operation from a single ,power line voltage,- and inmany cases the last mentioned motors 'are'actually provided with twofield windings. It should be notedas a feature of the invention thatboth field windings are used for operation on 110 volts and .220 volts.The elimination of the voltage dropping resistors which necessarily mustbe of high wattage rating considerably reduces the expense of theapparatus. In addition, the elimination of these resistors does awaywith unnecessary power loss, and the accompanying heat dissipationthereby enabling the construction of a more com- :pact phonographapparatus without causing overheating of'other components. The onlyadditional components required -by the present system, not required in aphonoigraph system for operation for a single power line voltage,

-is the provision of monster changing the connection of the fieldwindings from series to parallel.

It can be seen that in accordance with the invention,

this new and improved electric phonograph circuit efleo' :tivelyprovides for operation on two or more ditferent 'lin e voltages andutilizes the operating or field windings lot the driving motor as anauto-transformer for deriving the proper power line voltage for theself-contained audio frequency amplifier. This system, as has beenshown, may utilize components already a part of an electrical phonographdesigned for operation from a single power line voltage and does nothave the disadvantage of unnecessary power loss and the problem of heatdissipation.

What is claimed is:

1. An electric phonograph system for operation at one or more diiferentalternating current power line voltages comprising in combination, anaudio frequency amplifier adapted to be energized at a predeterminedalternating current voltage, a phonograph motor having a pair ofoperating windings, means for connecting said operating winding tooperate in parallel for a first power line voltage and in series for asecond high power line voltage, and means providing a fixed connectionfor said amplifier in parallel with one of said operating windings.

2. An electric phonograph system for operation at a first and a secondalternating current power line voltages comprising in combination, anaudio frequency amplifier adapted to be energized at said firstalternating current power line voltage, a phonograph motor having a pairof operating windings, means for connecting said operating windings inparallel for operation of said first power line voltage, means forconnecting said operating windings in series for operation on saidsecond power line voltage, and means providing a fixed connection forsaid amplifier in parallel with one of said operating windings.

3. An electric phonograph system for operation at a first and a secondalternating current power line voltages comprising in combination, anaudio frequency amplifier adapted to be energized at said firstalternating current power line voltage, a phonograph motor having a pairof operating windings, manual switching means for alternativelyconnecting said operating windings in parallel for operation of saidphonograph at said first power line voltage or in series for operationat said second power line voltage, and means fixedly connecting saidamplifier in parallel with one of said operating windings.

4. -An electric phonograph system as defined in claim 3, wherein saidmanual switching means comprises a doublepole, double-throw switch.

5. A power supply circuit for use with phone-graphs of the type whichinclude an audio frequency signal ampli fier and which are adapted tooperate with one or more different alternating current power supplyvoltages comprising, a phonograph motor having a pair of field windings,connection means for connecting said field windings with an alternatingcurrent power supply circuit, manual switching means for alternativelyconnecting said field windings in parallel for operation of saidphonograph at a first power supply voltage or in series for operation ata second power supply voltage, and means fixedly connecting saidamplifier in parallel with one of said operating windings.

6. A power supply circuit for use with phonographs of the type whichinclude an audio frequency signal arnplifier and which are adapted tooperate on power line voltages of either or 220 volts A. C., comprisinga phonograph motor having a pair of like field windings, connectionmeans for connecting said field windings with an alternating currentpower line, manual switching means for alternatively connecting saidfield windings in parallel for operation of said phonograph at the powerline voltage of 110 volts A. C. or in series for operation at thepowerline voltage of,220 volts A. C., and means fixedly-connecting saidamplifier in parallel with one of said operating windings.

7. A power supply circuit for use with pho-nographs .as defined in claim6 wherein said manual switching means comprises a'double-pole,double-throw switch.

Kneisley May 9, 1939 Anderson et a1. -J an. 18, 1949

